Pump Protection – Low Pressure Valves: Watch & Learn

With our SCHROEDAHL low pressure valves; the SUL and the TDL properties such as functionality, places of operation, valve specifications and the delimitations to each other, clearly indicate the valve that best meets your needs.

The SUL, our evergreen valve in the lower nominal pressure range up to 63 bar with a pressure difference of up to 40 bar.

The SUL is used in chemical process plants, for fire extinguishing pumps and also in power plants of all kinds where large volume flows are part of the day-to-day business.

It’s simple, solid design makes the SUL virtually indestructible.

Essentially, the SUL consists of the housing, the upper housing part and the bypass-inserts We consider the housing and the bypass-inserts as the “valve intelligence”.

AUTOMATIC PUMP FUNCTIONING

How the automatic pump protection for centrifugal pumps works using our SUL valve as an example.

SUL

The flow image shows the bypass system circuit in a Schroedahl valve. The medium, which is mostly feed water but can also be individual process media, is fed to the pump. This conveys the medium through the Schroedahl fitting and a downstream valve to the turbine or to an alternative process. A bypass branches off from the SCHROEDAHL fitting and connects the pump directly to the tank Three flow meters are used as a guide to the volume flow ratios.

Flowmeter 1, marked by red, indicates the percentage of the maximum flow rate applied to the pump.

Flowmeter 2 in blue represents the percentage of the maximum flow rate that is fed to the process.

And flowmeter 3 in green shows the volume returned to the tank.

BYPASS OPERATION

Flowmeter 2 displays 0% when no medium is being fed into the production process. The bypass of the automatic pump protection valve is in the fully open state It feeds the medium through the valve to the tank and back into the “pump circuit”.

Here flowmeter 1 and flowmeter 3 show the same maximum flow rate value of 30%.

The conical system, which is precisely adapted to the system requirements, closes the valve so that no medium is passed into the production process.

Flowmeter 2 shows 0%.

START UP

When the plant is started the valve responds by supplying the flow rate necessary for the production process entirely through its design without the measuring units required in conventional valves. The check valve lifts and opens the valve. The medium passes through the SUL to the turbine or to the downstream process. The difference between process and pump volume flow is balanced by the bypass.

CLOSED BYPASS

When a predetermined process volume is reached the bypass reaches its closed position. The pump feed rate and the process flow are now identical.

FULL LOAD – fluctuating load

If fluctuating loads are now encountered, the automatic pump protection valve automatically adapts itself to the situation without the need for additional control units. It continuously and robustly monitors the flow rate ensuring the smooth operation of the plant.

The SUL properties:

• It is produced from high-quality carbon steel or stainless steel The result is a valve that is flexible any yet suitable for robust applications.
• The nominal width range are from DN 25 to a maximum of DN 250
• The pressure stage for the SUL is designed up to PN 63.
• The range of application of the SUL valve is extended by the largest possible flow rates

Our SUL is the ideal and price-efficient valve for modern chemical processing plants and power plants where a highly variable flow rate is part of the daily business

The TDL

TDL, our universal genius for pressure differentials of up to 40 bar and nominal widths up to DN 500

• Reliable, modulating and low-maintenance,
• The TDL is suitable for all types of media.
• The TDL has a bypass unit flanged to the side of the housing

The precision non-return valve, which is specifically designed for your plant, controls the flow rate.

Using forged steel in the design enables a significantly higher nominal pressure to be achieved than with the SUL.

The image shows clearly how the check valve is lifted by the increased flow rate during start-up /shutdown process and how the medium is released to the process. The lever automatically adjusts and opens the bypass precisely at planned flow rates.

When the bypass is fully closed the entire flow rate is fed to the process.

The TDL properties:

• The TDL is produced from high-quality carbon steels, stainless steels, low-temperature steels and duplex steels
• The result is a valve that is flexible and yet suitable for robust applications. Media at temperatures of between -196 and + 300 degrees Celsius can be processed without problem.
• The nominal width ranges from DN 25 to a maximum of DN 500
• The TDL is designed up to PN 100

TDL valves are to be found mainly in chemical processes, but it is also a very reliable partner when used in the power plant industry.

More Information

For more information on our SCHROEDAHL pump protection low pressure valves please visit our website at https://bit.ly/3xoV9wV or call us at 1-800-912-9262.

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